1. Field of the Invention
The invention relates to a drive device for moving the end fitting of a passive safety belt along a predetermined motion track which has track sections extending at an angle to each other, by means of a flexible pulling and pushing means which can be driven by a drive and is coupled to the end fitting to be moved.
2. Description of the Prior Art
Flexible drive devices are known, for instance in the form of a bowden cable in which the pulling means proper consists of a flexible steel or plastic cable which is formed in a tubular sleeve part and which is driven by hand or by a motor. Such a drive device can be installed in any desired manner, the flexibility of the pulling means determining the magnitude of the possible deflections or bends. When under tensile as well as compression stress, large sliding friction forces occur at the deflection points which set relatively narrow limits to the drive system, especially under the influence of heavy temperature variations. As already indicated, a substantial disadvantage of such drive systems is that, when the pulling means is moved in curves with a relatively small radius of curvature, very high friction forces occur which lead to increased wear at the pulling means as well as at the guide and require a large amount of driving power. In passive safety belt systems for motor vehicles it is known to make the end fitting parts of the belt movable in the motor vehicle along a guide in such a manner that, before the person to be protected boards the vehicle, this end fitting point is at first in the vicinity of the so-called A-post and, during or after the boarding, is moved along a guide track into the vicinity of the B-post. For this purpose, customarily, drive devices are used, for instance in the form of flexible flat plastic belts or in the form of plastic-jacketed steel cables. Here, too, the described disadvantages appear.